Radio tuning system



Feb. 2 5, 1936. e. B. MARSDEN RADIO TUNING SYSTEM Original Filed March 5, 1930 4 Sheet s-Sheet 1 Feb. 25, 1936. G. B. MARSDEN RADIO TUNING SYSTEM Original Filed Mafch 5. 1930 4 Sheets-Sheet 2 Geo/59 W Feb. 25, 1936. e. B. MARSDEN RADIO TUNING SYSTEM Original Filed March 3, 1950 4 Sheets-Sheet 5 5 w 8 2 J A 7 7 My? Z w J w Z 15 a a 1 V w T 0 0 0 Q 5 a DH Y Z o a 6 6 Z 7wen/iol Feb. 25, 1936. G. B. MARSDEN 2,031,841

RADIO TUNING SYSTEM Original Fi-led March 3, 1950 4 Sheets-Sheet 4 A rlz weniol."

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Patented Feb-25, 1936 Z,03l,84l

UNITED STATES PATENT OFFICE RADIO TUNING SYSTEM George B. Mandel, Loo Angelel, Calif. Application March 3, 1930, Serial No. 432,810 Renewed March 28, 1935 2 Claims- (Cl. 74-10) This invention relates to improvements in radio pulleys of varying radii operated by a single belt, tuning apparatus, and more particularly to multichain, or the like. circuit radio apparatus having a single control One of the objections to this form of apparatherefo'r. tus from the standpoint of large quantity produc- In a prior application, bearing Serial No. 322,- tion, is that a pinion or pulley with a particular 5 345, filed November 28, 1928, of which this apsized radius must be cut for each circuit in every plication is a continuation in part, I have disreceiving set, or else large stocks of assorted sizes closed an improved method of tuning, and apmust be kept on hand to be used as required. paratus for applying the same, whereby two or In a second application, Serial No. 404,561, filed w more circuits may be continuously held at reso- November 4, 1929, I disclose an improved method 0 nance to mutual wavelengths by means of a of tuning based upon the same general principle single control without necessitating the matching of pro'ducing geared connections for each circuit of the inductance capacity values of the individual whereby the variation in the rate of movement of circuits. such condensers may be first determined by As in the prior application referred to, the formula, as before, but the resultant ratio is espresent invention is based upon the principle that tablished by simple rectilinear adjustments of there is a direct relationship between the angles certain part O the connecting mechimism- The of rotation of the sets of variable condenser plates second apparatus referred to, includes a plurality of any two rotatable condensers of the same type of Similar equi at al triangular Structures each from the positions where their respective cirhaving two legs of identical length. The desired cults are tuned to a minimum wavelength ratio of movement of any two condensers was (i=2l5 meters or thereabouts) to the positions provided by adjusting the lengths of each pair of where their respective circuits are mutually tuned legs so as to change the sizes of the respective to a higherwavelength 0:500 meters or theretriangular structures in accordance with the abouts), and that the respective angles of rotavalue of the constant (V) obtained, as before, by tion vary with the angle of rotation of the sets initially determining by temporary dials, or their of plates having the lesser rotation at a rate equivalent, the difference in angles of rotation of equal to a constant (V), multiplied by some power the two sets of plates between a lower and higher of the mutually resonant wavelength, said power wavelength to which the two circuits are mutu- 0f the wavelength depending upon the design of ally tuned. 30 the condensers employed. However, both forms of apparatus disclosed in I have demonstrated that this relationship is the two prior applications above referred to, refound to exist wherever the tuning condensers are quire the predetermination of the value of the p of identical design, that is, are all either of ratio of the angular displacements at resonance straight line wavelength, straight line frequency, and a. computation of the proper lengths of radii, 35 straight line capacity, or some compromise, and or adjustable legs of a triangular structure by customary mechanical precision is used in their means of a very accurate measurement to deterconstruction. mine these lengths. and then a proper manual The apparatus disclosed in the prior applicaadjustment of the parts connected to the common tion abo've referred to, provided a means for decontrol while both circuits are tuned to mutual 40 termining the required correction constant (V) resonance, all of which requires time, and prefor any two circuits by initially determining with sents opportunities for error both in the mathtemporary dials, or their equivalent, the difierematical computation and in the manual adence in angles of rotation of the two sets of plates justments of the apparatus. between a lower and higher wavelength to which In carrying out the present invention, I pro- 45 the two circuits are successively tuned; and then vide an improved and simplified form of operatby reference to the proper formula, the necessary ing connection for the several condensers wherecorrection constant could be provided by estabby the proper ratio is automatically given to the lishing a permanent geared operating connection adjustable parts during the adjustment of each for the two condensers having a. constant ratio circuit to a mutual resonance with the other cir- 50 which satisfies the formula above referred to. cult, so that thereafter all circuits remain at mu- The specific geared connections shown in my tual resonance with any simultaneous rotation prior application, comprise either two segments through the unitary control member. Thereof, varying radii connected to the separate confore, the time required to adjust any receiver, is densers and operated from a single rack, or only that time which would be required to tune 55 said receiver to only one mutually resonant wavelength with an individual control in each circuit, and the possibility of error in such adjustment has been reduced to an absolute minimum.

As will also more fully appear, my improved form of operating connection is equally applicable to condensers of the rotary and rectilinearly variable types.

The invention may best be understood by reference to the accompanying drawings, in which -Figure 1 is a skeletonized view of a radio receiving set showing the operating connections to two condensers of the rotor type.

Figure2 is a side view of the apparatus shown in Figure 1. I

Figures 3, 4a and 4b are a series of diagrams illustrating the principle of operation of the tuning adjustments forming the basis for the present invention.

Figure 5 is a detail of the thumbscrew adjusting device used in the apparatus shown in Figures 1 to 3, inclusive.

Figure 6 is a side view showing a modified form of my invention asapplied to a plurality of condensers mounted end to end in a shielded compartment.

Figure I is a front end view of the apparatus shown in Figure 6.

Figure 8 is a section taken on lineB-l of Figure 6.

Figure 9 is an enlarged detail of the thumbscrew adjusting device used in the apparatus shown in Figures 6 to 8 inclusive.

Figure 10 is a section taken on line llllll of Figure 9.

Referring now the embodiment to Figure 1, it will be seen that extending radially from the axis of rotation of said segment, and at an angle of to each other. A similar pair of grooves l9 and 29 is provided in the segment IS.

A rack i0 is mounted for lateral movement on the face of the plate ii in a plane equidistant above the axes of rotation of the two segments,

.and suitable gearing connection is provided for moving said rack by means of the unitary manual control.

In the form shown, said manual control means includes an operating stud shaft 1 having a hand control knob of the usual form (not shown) thereon and provided with a pinion 1a meshed with a gear segment 8 which is relatively large and is adapted to have an indicator dial 8;: suitably mounted thereon in the usual manner and provided with calibrations for tuning the set. The dial segment 8 is rotatably mounted on a stud 9 and has a pinion 9a carried of my invention therein dis-' thereby which meshes with teeth we carried on the under side of the rack Ill.

The rack l I is suitably guided for lateral movement, as for instance, in a longitudinal slot lilb supplemented by auxiliary rollers llo-lllc mounted on the face of the plate Ii. A pin it is carried on the rack ll of the segment l2, while a similar pin ll projects into slot I! on segment II so that a lateral motion of rack i0 caused by movement of the control shalt I causes a uniform rotation of the operating segments l2 and I3.

The arrangement shown in the drawings is such that the dial gear segment I is rotated through an angle of substantially while the pins II and. i5 move the full length of their respective slots l8 and I9 to rotate the segments i2 and It at equal rates through substantially 60.

Two racks 20 and 2| are mounted on the plate I to move in a line parallel with the movement of rack 10 and are provided with teeth 20a and 2 i a which respectively mesh with pinion segments 22 and 23 on condenser shafts 5a and a. respectively. A stud i1 is fixed on the right-hand rack 2| and projects into the slot 28 of segment IS. A pin it is mounted on rack 20 so as to be adjustable vertically thereof,. and extends into the slot 28 of segment l2.

Any suitable means of adjustment of the latter pin It may be provided, in the form shown in detail in Figure 5, said pin projecting laterally from one prong of a U-shaped member II which the vertical grooves 1|, 3| on a bracket 20b forming part of rack 20. A

cross bar lib is connected to the outer end of pin it. The position of the pin II is adjustable by thumbscrew 24 connected between the cross bar lia and a flange 32 on the lower edge of bracket 20b, the thumbscrew being thus arranged so as to shorten or lengthen the distance from pin ii to the axis of the segment l2. The ad- .lustment means just described is such that if the segment I2 is held from rotation, manipulation of the thumbscrew 24 in one direction or the other tends to shift the rack 20 to the right or left, and thereby change the positions of the two sets of condenser plates relative to each other.

In the initial position of the apparatus preparatory to tuning the same, the pins II and H are preferably arranged in the same horizontal plane at equal distance from the axis of rotation of the segments 12 and I: so as to hold said segments in identical angular positions. The pins- II and I! are then at the extreme outer ends of the slots l8 and i9, respectively, and the condenser plates are at such position of minimum capacity that 01 and 62 are both zero, all as shown in Figure 1. In this position, the indicating dial la also indicates a reading at zero.

With the details of the operating mechanism illustrated in Figures 1 and 2 now in mind, it may be well to review the principle of operation of my tuning system as originally'disclosed in my prior application, Serial No. 322,345. Following the mathematical development of this principle, it will then be manifest how the thumb screw 24 may be adjusted so as to vary the rates of rotation of the condensers 5 and I in such a manner as to maintain mutual resonance throughout the broadcasting range.

For convenience. two circuits employing straight line wave length condensers will be considered. The circuits may be numbered 2 and whose respective components have the subscripts s and 1- Cd: and C41 are the condensers.

C: and C1 are the condenser capacities.

c: and or are the circuit distributed capacitiesconstants.

Ia and Li are the actual coll inductances-also constants.

La: and Lin are the eflective inductances.

h and A1 are the respective wave lengths of resonance.

A is the wave length of mutual resonance where M=A1.

112, m, k, a, and V are electrical constants.

Q is a constant of integration.

0: and 01 are the angular displacements of the condensers.

Basic formula (For reference see U. 8. Bureau of Standards Circular No. '74.)

Therefore, at mutual resonance A where M=M, it follows that,

(2) foams-0 And differentiating (2), gives Interpreting Formula (3)since a: and or are constants, the rate of change in angular displacement of one set of rotary condenser plates varies with respect to the rate of change in angular displacement of the other set of condenser plates, as both circuits are constantly held at mutual resonance as the mutually resonant wave length is varied, and is equal to a constant times the square root of the rate of change in effective inductance in the one circuit with respect to the rate of change in the eflective inductance in the other circuit.

Therefore, if the rate .of change in effective inductance in the one circuit..varies with respect to the rate of change in the effective inductance in the other circuit at a constant rate as both circuits are held at mutual resonance, it is evident that the rate of change in the angular displacement of one set of condenser plates with respect to the rate of change of the angular displacement of the other set of plates must also be a constant rate.

At mutual resonance where 7u=7u differentiation of (C) gives,

Since all of the quantities in the right member of (5) are constants, the right member of (5) is a constant which shows that the rate of change in the effective inductance in one circuit varies with respect to the rate of change in theeffective inductance in the other circuit, as both circuits are continually held at mutual resonance at a constant rate and therefore it follows that by (3) and (5).

a constant value.

And integrating (8) gives (7)- cuits will be tuned to the minimum wavelength of mutual resonance and if both sets of plates are then caused to rotate in such a manner that Formula (6) is satisfied, it follows that both circuits will mutually tune to resonance for all wavelengths up to the maximum wavelength obtainable or where the plates of the condenser having the greater angular displacement will have reached their position of maximum capac ity.

Referring now more particularly to the operation of the adjusting mechanism forming the subject matter of the present invention, it will now be shown that a single adjustment canv be made in the position of the pin it so as to give, automatically, the proper ratio or variation in the rate of movement of the two condenser shafts 5a and 8a, which ratio satisfies the formula for the constant (V) as above developed.

From Figure 1 it'will be apparent that where segments I2 and I! must always rotate at equal rates and the movements of racks 20 and 2| are in the same horizontal line where pins I6 and I! are at the same distance from the centers of their respective segments at their initial equiangular positions (and in lines that are parallel when they are at unequal distances from their centers) the line 'of motion of pin I6, its distance to the axis of segment I! at'its initial position and its distance to the axis at its position after any rotation of segment l2, describe the three sides of a scalene triangle.

Similarly, the line of motion of pin I1 and its initial and final distances fromthe axis of segment l3, describe a similar triangle. The two triangles thus described will be identical where the initial distance of pin it from the axis of segment I! and of pin I! from the axis of segment 13 are equal.

Referring now'to the diagrams shown in Figure 3, 0 represents the axis of segment [2, P represents the point where a vertical line through 0 meets the extended line of motion of pin It, and Q is the position of pin it after a given rotation of segment I! so that OPQ forms a right triangle. Likewise, O'MN of Figure 3' forms a similar right triangle described by a similar movement of pin I1 and segment I3. Let 11 equal the distance of pin Iii from O or 0Q, and 1': equal the distance of pin l'l from 0' and let OP and OM be equal to hi and hz, respectively.

From the construction it is evident that the values of hi and ha will remain constant for all values of n and r: given by different rotations of i2 and i3 simultaneously, and

(8) r1=h1 sec. R and rz=hz sec. R.

( n h: s

And since hi and h: remain constant, the ratio of n to r: and vice versa remains constant for any value of R.

In Figure 4a the triangles OSQ and OS'N represent the movements of racks 20 and II from their initial positions when thumbscrew N has been adjusted so that IE and ll are at equal distances from their respective centers to a point where 20 has moved through a distance QS and 2| has moved an equal distance :cz.

Since pinions 22 and 23 have equal radii, the lateral movement of racks 20 and 21 or an and :22, respectively, will represent the arcs subtended by 01 and 02, and since by geometry the ratio of arcs subtended on equal circles is equal to the ratio of their central angles,

X2 (10) i i Now considering Figure 4a: Suppose that when pin H has moved the distance an, it is found that circuit 2 is resonant to A: but that circuit 1 is resonant to M which is greater in value than X2. It is apparent that to make both circuits mutually resonant to A2, QS will have to be reduced by some amount thus reducing the value of 01 while the values of an and 62 remain fixed.

Consider the control shaft 1 held firmly so that segments l2 and ii are unable to rotate as thumbscrew 24 is turned, so that pin I6 is raised to the point '1 in Figure 4a where it is found that both circuits are mutually resonant to M. n will then have been reduced in length from Q to 0'1 and as will then havea value equal to that which rack 20 is moved through as the segments are turned back by control shaft 1 to the point where 01:0, as shown by the dotted line TU which forms the base of the triangle OTU of Figure 4a..

It is evident from Figure 411 that as the control shaft is turned back, the pin I! will not come back to its initial position but to a point Y. Where YS equals 2 and the motion of rack 2| is 13-2, 0: will then have a value greater than 0 when 01 is equal to 0.

In Figure 4b the triangles OTU and ONY of Figure 4a are shown in superposed relation. From this figure it is evident that,

eg -5 1 :2 1 1'1 I1 But when 01 is equal to zero by construction, :21 is also zero and z=:z:z and (2:02

Hence as 01 approaches the value zero and :01 likewise approaches the value zero, Formula (13) approaches nearer and nearer the value 2 1-- e l l l until the difference between 1 h w x1 and 01 will become less than any value, however small, and

And since the ratio of 1': to 1'1 is a constant by (9) and V is a. constant, it follows that (14) must hold true for any value of 91 and corresponding value of x Therefore, by (13) and (14) Multiplying the left member of (15) by and the right-hand member by I gives Which shows that when :r: is equal to z, 0: is equal to Q which by the interpretation of (7) shows that the two circuits will be mutually resonant to their minimum mutual wavelength when the control shaft I is turned back until 0 is at zero. Since the ratio of the angular displacements must remain at aconstant value equal to V by (14) the interpretation of ('7) shows further that the circuits must remain resonant to a mutual wavelength with any angular rotation of I! and I3, through any movement of the unitary control shaft I.

Should it be necessary to increase the value of xi instead of decreasing it to attain mutual resonance, thumbscrew 24 would be turned in the opposite direction and the Proof would have been substantially the same.

In securing resonance with a single adjustment screw to vary the radial length of the pinion it is preferable that the angles A and B in Figure 40 must have a value of 90 or more at the points of minimum capacity where 0: or 01 is equal to zero when M=M.

In actual practice in tuning a superheterodyne, as was herein described for sake of brevity, where an adjustable device is placed on but one condenser circuit segment, l2, the control is preferably placed on the antenna circuit, as it is not in most instances as sharp in tuning as the oscillator circuit and will pass sufficient current to make it possible to readily detect the point where the oscillator circuit is resonant to a given'frequency, although the antenna circuit may be resonant to a frequency thirty or forty kilocycles different.

Where the tuning method above described is applied to a tuned radio frequency receiver, suitable auxiliary adJustment controls corresponding to parts It, 24, and 30 are provided for each circuit segment corresponding with part II, and the receiver may then be tuned to any relatively low wavelength by the individual adjustment screws 24, without changing the position of unitary control knob I. The set will then be synchronized so that movement of-the control knob will tune all the circuits at all wavelengths within its normal range.

If it is desired that the indicator dial 8a read exactly zero at any particular frequency, as for instance, 1500 kilocycles, afkl the set has been synchronized as described and tuned to that particular frequency, the condenser shafts a and 50 :may be temporarily fixed by any suitable means such as set screws 55 in collars 55 encircling the shafts and fixed on the frames of condensers 5 and 5. then released by loosening their respective set screws 22c and 25a. The control shaft 1 can then be turned back until zero reading is obtained on the dial 5a, the pinion set screws retightened, and the condenser shaft clamping screws 55, -25 released,

It will be especially noted in connection with the construction and arrangement shown in Figure 1, that the rate of rotation of each of the condenser shafts is greater when the condensers are near their minimum capacities than at their maximum capacities. This is due to the interposition of a pivotal segment such as segment i2 between rack l5 and rack 25, which results in producing the effect of spreading out or separating the readings for the broadcasting channels at the lower range of wavelengths. This spreading of the lower broadcasting channels is particularly desirable where the condensers of the straight-line capacity type are used, which type of condensers, as is well known, ordinarily give the effect of crowding the lower wavelength broadcasting channels much more than the higher wavelength channels.

It will be manifest; however, that the initial angles of the operating segments may also be arranged to cause a greater rate of movement of the condensers near their maximum capacities,

and thus cause spreading of the higher broad-' cast channels,,or they may also be arranged at an intermediate position, so as to produce any desired compromise in spacing of the broadcasting channels about the indicating dial 5a.

Referring now to the modified form of my invention shown in Figures 6 to inclusive, it will be seen that my device is applied to a plurality of rotor type condensers 45, 45 arranged in axial alignment with each other in a shielding compartment or casing 45. The stators 41 are mounted on insulation blocks 41a, and the shafts 45a of rotors 45b are each journalled on supports 45c of any suitable construction.

An operating segment 52 is fixed on a shaft 53 extending along the top of the casing 46, and suitably journalled thereon as by brackets 53a. The segment 52 is provided with two grooves 54 and 55 extending radially thereof, and at an angle of 90 to each other. This segment and its grooves correspond to the similar segments l2 and I5 shown in Figure 1.

Means for oscillating the segment 52 may be similar to the arrangement shown in Figure l, and comprise an operating stud shaft 51 having a hand control knob of the usual form (not shown) thereon and provided with a pinion 51a meshed with a gear segment 58. Said gear segment is adapted to have an indicator dial 55a suitably mounted thereon and provided with calibrations for tuning the set. The dial segment is rotatably mounted on a stud 59 1 ournalled in the front wall 450. and having a pinion 59a on the inner end thereof which meshes with teeth 55a of a rack 55, suitably guided for vertical movement along the inner face of the front wall 45a and extending through the upper wall of the casing (see Figures 6 and 7). A pin 6| projects from the upper end of rack 65, and moves in groove 55 formed in the segment 5a (see Figure 7) The pinions 22 and 23 on said shafts are The arrangement shown in the drawings is such that rotation of the dial gear segment 55 through an angle of approximately 185 will cause the pin 55 to more the full length of slot 55' and rotatethe segment 52 and shaft 53 through substantially 65.

It will now be observed that the shaft 53 has a plurality of lever arms 52 fixed thereon, each provided with a slot 54 which is disposed at the same angle with the axis of said shaft as the slot 54 formed in the segment 52, as previously described. Thus, by rotation of the shaft 52, the slots 54 and 54 are all rotated in unison with each other.

Means are provided for adjustably connecting each of the condenser shafts with one of the identically disposed slots 54 and 54, through the medium of a rack 55, having a pin 5| at its upper end movable in its respective slot. As seen in Figure 8, the rack 55 is guided for vertical movement on the cross support 48 and is meshed with pinion 49 of condenser shaft 45a. In this sectional view, the condenser shown is the second condenser from the end wall'45a, and therefore has connection with a lever arm 52 and slot 54. The rack 55 of the condenser immediately adjacent the end wall 45a, as seen in Figure '7, has a similar rack 55, but it is directly connected with slot 54 of segment 52.

The adjustment of the apparatus is provided by independently shifting the position of the pins 5| at an angle to the normal angle of the slots 54 or 54 within which said pins are movable, and thus giving the same variation in rates of movement of the several condenser rotors, as is accomplished by adjustment of the pin IS in the form of device shown in Figures 1 to 3 inelusive.

. The modified form of adjustment shown in detail in Figures 9 and 10, comprises a thumbscrew 66 extending between wings 51 and 68, connected respectively to the rack 55 and its pin 5|, so as to adjust the position of the latter. In the form shown, the pin 5| is mounted on a plate 5Ia slidable on the inner side of bracket 55a integral with rack 55. A slot 55b is formed longitudinally of bracket 55a. Wing 55 is provided with a flanged portion 55a on the outer side of bracket 55a which is connected to the plate 5| by a block 59 slidable along the slot 55b, so that the wing 58 and pin 5| are movable as a unit relative to the rack 55 when adjusted by the thumbscrew 55. The adjustment thus provided, therefore, gives the same variation in angular positions of the several condenser rotors as is afforded in the form of apparatus shown in Figures 1 and 2, and the several circuits of the receiving set may be adjusted to mutual resonance in the same manner as already described throughout the broadcasting range of the set.

Although I have shown and described certain embodiments of my invention, it will be understood that I do not wish to be limited to the exact constructions shown and described, but that various changes and modifications may be made without departing from the spirit and scope of my invention as defined in the appended claims:

I claim:

1. In a unitary control tuning system, a control member, a plurality of circuits each tuned by a variable condenser, relatively adjustable intermediate driving connections ior each of said condensers comprising similar pivotally movable members rotatable by said control member at uniform rates, and a rectilinearly movable condenser operating member oonnectible with each of said pivotally movable members, and means adjusting at leastone of said rectilinear movable members at points along a. radial line 0! its respective pivotal member to vary the effective radii of said pivotally movable members at ratios determined by mutually tuning their respective circuits to the same wavelength. I

2. In a unitary control tuning system, a control 1 member, a. plurality of circuits each tuned by a variable condenser, relatively adjustable intermediate driving connections or each of said condensers comprising similar pivotaliy movable members rotatable by said control member at uniform rates, and a rectilinearly movable condenser operating member adjustabiy connectibie with said pivotally movable members at points along a radial line of the latter to vary the eflective radii of said pivotally movable members. 

